placement: Update go-yaml version (pingcap#25815)

ddl/placement/rule.go

@@ -17,7 +17,7 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/go-yaml/yaml"
+	"gopkg.in/yaml.v2"
 )
 
 // PeerRoleType is the expected peer type of the placement rule.

go.mod

@@ -17,7 +17,6 @@ require (
 	github.com/fatih/color v1.10.0 // indirect
 	github.com/fsouza/fake-gcs-server v1.17.0 // indirect
 	github.com/go-sql-driver/mysql v1.5.0
-	github.com/go-yaml/yaml v2.1.0+incompatible
 	github.com/gogo/protobuf v1.3.2
 	github.com/golang/protobuf v1.3.4
 	github.com/golang/snappy v0.0.2-0.20190904063534-ff6b7dc882cf
@@ -78,6 +77,7 @@ require (
 	golang.org/x/tools v0.1.4
 	google.golang.org/grpc v1.27.1
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
+	gopkg.in/yaml.v2 v2.4.0
 	modernc.org/mathutil v1.2.2 // indirect
 	sourcegraph.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0
 	sourcegraph.com/sourcegraph/appdash-data v0.0.0-20151005221446-73f23eafcf67

go.sum

@@ -194,8 +194,6 @@ github.com/go-sql-driver/mysql v1.4.1/go.mod h1:zAC/RDZ24gD3HViQzih4MyKcchzm+sOG
 github.com/go-sql-driver/mysql v1.5.0 h1:ozyZYNQW3x3HtqT1jira07DN2PArx2v7/mN66gGcHOs=
 github.com/go-sql-driver/mysql v1.5.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
-github.com/go-yaml/yaml v2.1.0+incompatible h1:RYi2hDdss1u4YE7GwixGzWwVo47T8UQwnTLB6vQiq+o=
-github.com/go-yaml/yaml v2.1.0+incompatible/go.mod h1:w2MrLa16VYP0jy6N7M5kHaCkaLENm+P+Tv+MfurjSw0=
 github.com/goccy/go-graphviz v0.0.5/go.mod h1:wXVsXxmyMQU6TN3zGRttjNn3h+iCAS7xQFC6TlNvLhk=
 github.com/gogo/protobuf v0.0.0-20171007142547-342cbe0a0415/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/gogo/protobuf v0.0.0-20180717141946-636bf0302bc9/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=